[PATCH v5 2/3] kernel/resource: Refactor __request_region to allow external locking

[Alistair Popple]

Refactor the portion of __request_region() done whilst holding the
resource_lock into a separate function to allow callers to hold the
lock.

Signed-off-by: Alistair Popple <apop...@nvidia.com>
---
 kernel/resource.c | 52 +++++++++++++++++++++++++++++------------------
 1 file changed, 32 insertions(+), 20 deletions(-)

diff --git a/kernel/resource.c b/kernel/resource.c
index 736768587d2d..75f8da722497 100644
--- a/kernel/resource.c
+++ b/kernel/resource.c
@@ -1181,31 +1181,16 @@ struct address_space *iomem_get_mapping(void)
        return smp_load_acquire(&iomem_inode)->i_mapping;
 }
 
-/**
- * __request_region - create a new busy resource region
- * @parent: parent resource descriptor
- * @start: resource start address
- * @n: resource region size
- * @name: reserving caller's ID string
- * @flags: IO resource flags
- */
-struct resource * __request_region(struct resource *parent,
+static int __request_region_locked(struct resource *res, struct resource 
*parent,
                                   resource_size_t start, resource_size_t n,
                                   const char *name, int flags)
 {
        DECLARE_WAITQUEUE(wait, current);
-       struct resource *res = alloc_resource(GFP_KERNEL);
-       struct resource *orig_parent = parent;
-
-       if (!res)
-               return NULL;
 
        res->name = name;
        res->start = start;
        res->end = start + n - 1;
 
-       write_lock(&resource_lock);
-
        for (;;) {
                struct resource *conflict;
 
@@ -1241,13 +1226,40 @@ struct resource * __request_region(struct resource 
*parent,
                        continue;
                }
                /* Uhhuh, that didn't work out.. */
-               free_resource(res);
-               res = NULL;
-               break;
+               return -EBUSY;
        }
+
+       return 0;
+}
+
+/**
+ * __request_region - create a new busy resource region
+ * @parent: parent resource descriptor
+ * @start: resource start address
+ * @n: resource region size
+ * @name: reserving caller's ID string
+ * @flags: IO resource flags
+ */
+struct resource *__request_region(struct resource *parent,
+                                 resource_size_t start, resource_size_t n,
+                                 const char *name, int flags)
+{
+       struct resource *res = alloc_resource(GFP_KERNEL);
+       int ret;
+
+       if (!res)
+               return NULL;
+
+       write_lock(&resource_lock);
+       ret = __request_region_locked(res, parent, start, n, name, flags);
        write_unlock(&resource_lock);
 
-       if (res && orig_parent == &iomem_resource)
+       if (ret) {
+               free_resource(res);
+               return NULL;
+       }
+
+       if (parent == &iomem_resource)
                revoke_iomem(res);
 
        return res;
-- 
2.20.1